Quantum singularities were studied for different specific situations (and using also generalizations), mainly using the first approach [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}. Recently, singularities in f(R) gravity were investigated in the presence of linear electromagnetic field [14]}.
